1. Field of the Invention
The present invention relates to a coil component obtained by winding a winding around a drum-shaped core and coating the winding with a resin, and a method of manufacturing the same.
2. Related Art
The coil component obtained by winding the winding around a winding core portion of the drum-shaped core and coating a resin with magnetic powder, obtained by mixing a magnetic particle with a resin, on an outer periphery of the winding is used in a DC/DC converter of a portable electronic device and the like (for example, refer to the Japanese Patent Application Laid-Open No. 2008-205245).
Recently, with small-sizing of the electronic device, the coil component of this type has been frequently used. Since a thermal expansion rate of the resin with magnetic powder, which coats the winding, and that of the drum-shaped core are different from each other, such coil component might be fatigued by change in stress by a temperature and finally, a core thereof might be broken.
FIG. 3 is a cross-sectional view of a conventional coil component 9. A winding 5 is wound around a winding core portion 1 of a drum-shaped core 4 formed of ferrite having a pair of flange portions 2 and 3 on both ends in an axial direction of the winding core portion 1. A space on an outer periphery of the winding 5 interposed between a pair of flange portions 2 and 3 is coated with a resin with magnetic powder 6.
In such coil component, since the thermal expansion rate of the resin with magnetic powder 6, which coats the winding, and that of the drum-shaped core 4 is different from each other, the resin with magnetic powder 6 expands to serve to extend the space between the upper and lower flanges when the temperature is high and the resin with magnetic powder 6 contracts to narrow the space between the upper and lower flanges when the temperature is low. As a result, there has been a problem of long-term reliability that the flanges 2 and 3 are fatigued to be broken.